Buggy code:
public class DOMNormalizer implements XMLDocumentHandler { protected static final boolean DEBUG_ND = false ; protected static final boolean DEBUG = false ; protected static final boolean DEBUG_EVENTS = false ; protected static final String PREFIX = "NS" ; protected DOMConfigurationImpl fConfiguration = null ; protected CoreDocumentImpl fDocument = null ; protected final DOMNormalizer . XMLAttributesProxy fAttrProxy = new DOMNormalizer . XMLAttributesProxy ( ) ; protected final QName fQName = new QName ( ) ; protected RevalidationHandler fValidationHandler ; protected SymbolTable fSymbolTable ; protected DOMErrorHandler fErrorHandler ; protected int fNamespaceCounter = 1 ; protected boolean fNamespaceValidation = false ; protected boolean fPSVI = false ; protected final NamespaceContext fNamespaceContext = new NamespaceSupport ( ) ; protected final NamespaceContext fLocalNSBinder = new NamespaceSupport ( ) ; protected final Vector fAttributeList = new Vector ( 5 , 10 ) ; protected final DOMErrorImpl fDOMError = new DOMErrorImpl ( ) ; protected final DOMLocatorImpl fLocator = new DOMLocatorImpl ( ) ; protected Node fCurrentNode = null ; private QName fAttrQName = new QName ( ) ; final XMLString fNormalizedValue = new XMLString ( new char [ 16 ] , 0 , 0 ) ; public DOMNormalizer ( ) { } protected void normalizeDocument ( CoreDocumentImpl document , DOMConfigurationImpl config ) { fDocument = document ; fConfiguration = config ; fSymbolTable = ( ( SymbolTable ) ( fConfiguration . getProperty ( SYMBOL_TABLE ) ) ) ; fNamespaceContext . reset ( ) ; fNamespaceContext . declarePrefix ( EMPTY_STRING , EMPTY_STRING ) ; fNamespaceCounter = 1 ; if ( ( ( fConfiguration . features ) & ( DOMConfigurationImpl . VALIDATE ) ) != 0 ) { fValidationHandler = singleton . getValidator ( XML_SCHEMA ) ; fConfiguration . setFeature ( XERCES_VALIDATION , true ) ; fConfiguration . setFeature ( SCHEMA , true ) ; fNamespaceValidation = true ; fPSVI = ( ( ( fConfiguration . features ) & ( DOMConfigurationImpl . PSVI ) ) != 0 ) ? true : false ; fDocument . clearIdentifiers ( ) ; ( ( XMLComponent ) ( fValidationHandler ) ) . reset ( fConfiguration ) ; } fErrorHandler = ( ( DOMErrorHandler ) ( fConfiguration . getParameter ( "error-handler" ) ) ) ; if ( ( fValidationHandler ) != null ) { fValidationHandler . setBaseURI ( fDocument . fDocumentURI ) ; fValidationHandler . setDocumentHandler ( this ) ; fValidationHandler . startDocument ( null , fDocument . encoding , fNamespaceContext , null ) ; } try { Node kid ; Node next ; for ( kid = fDocument . getFirstChild ( ) ; kid != null ; kid = next ) { next = kid . getNextSibling ( ) ; kid = normalizeNode ( kid ) ; if ( kid != null ) { next = kid ; } } if ( ( fValidationHandler ) != null ) { fValidationHandler . endDocument ( null ) ; <START_BUG> singleton . releaseValidator ( XML_SCHEMA ) ; <END_BUG> fValidationHandler = null ; } } catch ( RuntimeException e ) { modifyDOMError ( ( "Runtime<seq2seq4repair_space>exception:<seq2seq4repair_space>" + ( e . getMessage ( ) ) ) , SEVERITY_FATAL_ERROR , null ) ; this . fErrorHandler . handleError ( fDOMError ) ; if ( true ) { e . printStackTrace ( ) ; } } } protected Node normalizeNode ( Node node ) { } protected final void expandEntityRef ( Node node , Node parent , Node reference ) { } protected final void namespaceFixUp ( ElementImpl element , AttributeMap attributes ) { } protected final void addNamespaceDecl ( String prefix , String uri , ElementImpl element ) { } protected final DOMError modifyDOMError ( String message , short severity , Node node ) { } protected final void updateQName ( Node node , QName qname ) { } final String normalizeAttributeValue ( String value , Attr attr ) { } protected final class XMLAttributesProxy implements XMLAttributes { protected AttributeMap fAttributes ; protected CoreDocumentImpl fDocument ; protected ElementImpl fElement ; protected final Vector fAugmentations = new Vector ( 5 ) ; public void setAttributes ( AttributeMap attributes , CoreDocumentImpl doc , ElementImpl elem ) { } public int addAttribute ( QName qname , String attrType , String attrValue ) { } public void removeAllAttributes ( ) { } public void removeAttributeAt ( int attrIndex ) { } public int getLength ( ) { } public int getIndex ( String qName ) { } public int getIndex ( String uri , String localPart ) { } public void setName ( int attrIndex , QName attrName ) { } public void getName ( int attrIndex , QName attrName ) { } public String getPrefix ( int index ) { } public String getURI ( int index ) { } public String getLocalName ( int index ) { } public String getQName ( int index ) { } public void setType ( int attrIndex , String attrType ) { } public String getType ( int index ) { } public String getType ( String qName ) { } public String getType ( String uri , String localName ) { } public void setValue ( int attrIndex , String attrValue ) { } public String getValue ( int index ) { } public String getValue ( String qName ) { } public String getValue ( String uri , String localName ) { } public void setNonNormalizedValue ( int attrIndex , String attrValue ) { } public String getNonNormalizedValue ( int attrIndex ) { } public void setSpecified ( int attrIndex , boolean specified ) { } public boolean isSpecified ( int attrIndex ) { } public Augmentations getAugmentations ( int attributeIndex ) { } public Augmentations getAugmentations ( String uri , String localPart ) { } public Augmentations getAugmentations ( String qName ) { } } public void startDocument ( XMLLocator locator , String encoding , NamespaceContext namespaceContext , Augmentations augs ) throws XNIException { } public void xmlDecl ( String version , String encoding , String standalone , Augmentations augs ) throws XNIException { }

Fix:
singleton . releaseValidator ( XML_SCHEMA , fValidationHandler ) ;